1. Field of the Invention
The present invention relates to a light amount adjustment actuator unit used for a photographing apparatus such as a camera, a stepping motor which drives the lens group and the like of the photographing apparatus, an optical unit having them, and an electronic camera having the optical unit.
2. Description of the Related Art
Generally, for an optical unit in an electronic camera, a light amount adjustment mechanism which adjusts the light amount from an object, a lens group for obtaining a predetermined object image, and actuators and the like which drive the light amount adjustment mechanism and lens group are accommodated and fixed in one case.
For the optical unit in which all components such as the light amount adjustment mechanism, lens group, and actuators are integrally accommodated and fixed in one case, as described above, the assembly workability is poor, and therefore, assembly is time-consuming. In addition, adjustment after assembly is also cumbersome.
There is an actuator for driving a stop/shutter in a photographing apparatus such as a camera, in which a first actuator which drives a light shielding member and a second actuator which drives a light amount limiting member are separately arranged, as disclosed in Jpn. Pat. Appln. KOKAI publication No. 2000-310803 (paragraph [0006]; FIG. 1).
However, when two separate actuators are mounted in a photographing apparatus such as a camera, as described above, the space efficiency is low, and the apparatus becomes bulky. To avoid such an increase in apparatus size, a motor unit has been proposed in Jpn. Pat. Appln. KOKAI publication No. 11-234986 (paragraph [0038]; FIG. 13) in which two actuators are integrated, and shutter vanes and stop vanes are individually driven.
The shape of the motor unit disclosed in Jpn. Pat. Appln. KOKAI publication No. 11-234986 is long in the horizontal direction, as shown in FIG. 1 of this prior art, because two actuators are integrated. This poses restrictions on the member layout. For example, the members must be arranged in a circular shape around the optical path. A portable device such as an electronic camera requires an actuator unit that can be made as compact as possible without any restrictions.
On the other hand, the stator core of a lens driving stepping motor applied to a camera which is required to be compact is disclosed in Jpn. Pat. Appln. KOKAI publication No. 07-163126 (paragraph [0010]; FIG. 1) in which a plurality of cores formed by simply press-working a magnetic plate are separately arranged.
In the stator core using the core members manufactured by press working, as disclosed in Jpn. Pat. Appln. KOKAI publication No. 07-163126, a loss due to an eddy current is large, and the motor efficiency is insufficient. However, it has been supposed to be technically difficult to employ stacked cores as the stator core of a lens driving stepping motor which is required to be small because the object to be worked is very small.